This STTR project proposes to develop a novel optical scalpel for ultra-precise ophthalmic laser surgery. Segmentation and removal of epiretinal membranes during vitreoretinal surgery is currently performed mechanically with both blunt and sharp dissection, which causes collateral damage to healthy retinal tissue. Conventional fiber-based surgical laser microprobes used for thermal photocoagulation are unsuited for photoablation. Other reported optical scalpels have several disadvantages in intraocular laser surgery: 1) it is difficult to control the working distance, resulting in a variable laser spot size which may lead to unnecessary damage to adjacent retinal tissue;2) the treatment depth produced by the lensed and tapered fiber probes is excessively high, resulting in significant retinal damage below the focused spot;3) other probes cannot be used for contact surgery which allows for better surgical control and protection for adjacent tissue;and 4) air or perfluorocarbon liquid used by other probes presses epiretinal membranes to the retina, increasing the likelihood of collateral damage. Our proposed optical scalpel has the potential to address the limitations of current techniques and of other optical scalpels in development for improved ophthalmic surgery, by providing higher surgical precision, better control, and more ease of use. These improvements should result in better surgical outcomes. The proposed novel optical scalpel is designed for segmenting and delaminating fibrotic epiretinal membranes from the retina with small and well controlled depth in contact surgery. The optical scalpel also has other applications such as corneal surgery, lens removal, glaucoma filtration procedures, choroidotomy for subretinal fluid drainage, and vitreous removal. The optical scalpel is composed of a hollow waveguide infiltrated with chains of microspheres, providing periodical focusing of light with progressively smaller sizes of the focused beams. This design is based on properties of nanojet-induced modes observed recently in chains of polystyrene microspheres at the principal investigator's laboratory. The objectives of the Phase I project are to overcome the technical challenges of integrating microsphere chains into hollow waveguides, to develop a prototype optical scalpel, and to test the operation of this tool in ophthalmic tissues, ex vivo, using a mid-infrared Erbium:YAG laser for ultra-precise tissue ablation. If successful, these Phase I studies will position us for a Phase II study to develop this technology further for testing in an animal model, in vivo, and eventually for commercialization of the product. PUBLIC HEALTH RELEVANCE: This STTR project proposes to develop a novel optical scalpel for ultra-precise ophthalmic laser surgeries. The proposed novel optical scalpel is based on properties of nanojet-induced mode that the focused laser spots with progressively smaller sizes down to diffraction limit can be realized in a microsphere chain within an optical-guide.